Abstract. In this paper, the image characteristics of rectangular parts like plate analyzed in this paper in view of the demand for automatic truning plate in the rolling process. Image processing technology is used to identify the image, based on the edge detection algorithm, contour tracking algorithm and edge detection algorithm to achieve the size and angle of the rectangular parts of the plate. Based on the construction of the plate image detection and measurement system, the automatic turning plate control algorithm is developed, which realizes the automatic production process control of the plate plant, and meets the requirements of the process to produce rhythm control, and improves the production efficiency.